"The quality assurance (QA) of the consistency of radiation treatment delivery with the prescription is a continual concern, locally as well as nationally. The ROB employs graticules, projecting alignment and size information directly on both simulator films of the intended treatment fields and all corresponding portal images. This project is to overlay images from digitized simulator and port films, electronic portal images and digitally reconstructed segmental images from CT data in order to determine the accuracy and repeatability of radiation field alignment with respect to the target and critical anatomical structures. Currently a scanning laser densitometer has been acquired. This permits us to digitize both simulator and port films for comparison. Software for the digitizer also allows us to read and write files in the special formats necessary for our portal imaging unit, so that images can be utilized from this modality. Additionally we have developed software to acquire images film images from any imaging modality and to rotate and scale them so that they can be available for immediate comparison. Additional software has been developed to combine CT and MRI image data of any given patient to accurately determine target volumes. Current research involved the development of a multimodality external fiducial system for improving image registration accuracy. Addiaionally, the use of commercial digital imaging phosphor plates as a substitute for wet film emulsions in portal imaging is being explored."